This invention relates generally to wireless networks, and, more particularly, to methods and systems for cooperative transmission in multi-hop ad-hoc networks.
An ad-hoc network architecture is a network that can be deployed rapidly and without relying on preexisting fixed network infrastructure. Personal communications and mobile computing require a wireless network infrastructure that is fast deployable, possibly multi-hop, and such an infrastructure is provided by multi-hop ad-hoc networks.
Since the first appearance of wireless ad hoc networks as the DARPA packet radio networks in the 1970s, wireless ad hoc networks have been the subject of research and development and have been considered for a number of applications. Proposed applications of wireless ad hoc networks include, but are not limited to:                tactical operation—for fast establishment of communication infrastructure during force deployment in unknown and hostile terrain;        rescue missions—for communication in areas without adequate wireless coverage;        national security—for communication in times of national crisis, where the existing communication infrastructure is non-operational due to a natural disaster or a global war;        law enforcement—for fast establishment of communication infrastructure during law enforcement operations;        commercial use—for setting up communication in exhibitions, conferences, or sale presentations;        education—for operation of wall-free (virtual) classrooms; and        sensor networks—for communication between intelligent sensors mounted on mobile platforms.        
However, multi-hop network protocols are presently designed using the paradigm of packet Networks and of point to point communications. Messages are delivered by going through a series of intermediate nodes through point to point links forming a routing path. In many applications of ad-hoc networks the medium is broadcast; therefore to attain point to point communications it is necessary to perform a Multiple Access protocol and resolve the contention in using the medium. Once the access is granted to a source and destination pair, the Physical Layer functions (source/channel coding) that pertain to each link are done locally. There is a need for a cooperative form of transmission performed by a set of asynchronous transceivers operating as a distributed joint communication system.
The nodes in ad-hoc networks are generally designed with low power transmitters whose power often not sufficient for communication towards distant receivers. This problem is often referred to as the reach back problem in military applications and could have an important role in more general sensor network applications.
The trademark of the reach-back problem is that the information from an arbitrary network node cannot be forwarded to a receiver that does not have a relay node in its vicinity without quickly draining its energy resources. The reach back point is “disconnected” since there is no point to point link that can be established towards it. Surprisingly, even though it appears to be a very concrete problem, the reach back problem has not received a critical mass of attention. There is a need for methods and systems that provide means for communicating with distant receivers, that is, solutions to the reach back problem.